implemented

@@ -17,8 +17,62 @@
 
 #include "mail.h"
 
+static int is_terminal;
+
+#define COND_STK_SIZE 64
+#define COND_STK_INCR 16
+static int *_cond_stack;     /* Stack of conditions */
+static int _cond_stack_size; /* Number of elements allocated this far */
+static int _cond_level;      /* Number of nested `if' blocks */
+
+static void _cond_push(int val);
+static int _cond_pop(void);
+
+int
+if_cond()
+{
+  if (_cond_level == 0)
+    return 1;
+  return _cond_stack[_cond_level-1];
+}
+
+void
+_cond_push(int val)
+{
+  if (!_cond_stack)
+    {
+      _cond_stack = calloc(COND_STK_SIZE, sizeof(_cond_stack[0]));
+      _cond_stack_size = COND_STK_SIZE;
+      _cond_level = 0;
+    }
+  else if (_cond_level >= _cond_stack_size)
+    {
+      _cond_stack_size += COND_STK_INCR;
+      _cond_stack = realloc(_cond_stack,
+			    sizeof(_cond_stack[0])*_cond_stack_size);
+    }
+  
+  if (!_cond_stack)
+    {
+      fprintf(ofile, "not enough memeory");
+      exit (EXIT_FAILURE);
+    }
+  _cond_stack[_cond_level++] = val;
+}
+
+int
+_cond_pop()
+{
+  if (_cond_level == 0)
+    {
+      fprintf(ofile, "internal error: condition stack underflow\n");
+      abort();
+    }
+  return _cond_stack[--_cond_level];
+}
+	       
 /*
- * i[f] s|r
+ * i[f] s|r|t
  * mail-commands
  * el[se]
  * mail-commands
@@ -30,7 +84,89 @@
 int
 mail_if (int argc, char **argv)
 {
-  fprintf (ofile, "Function not implemented in %s line %d\n",
-	   __FILE__, __LINE__);
+  struct mail_env_entry *mode;
+  int cond;
+
+  if (argc != 2)
+    {
+      fprintf(ofile, "if requires an argument: s | r | t\n");
+      return 1;
+    }
+
+  if (argv[1][1] != 0)
+    {
+      fprintf(ofile, "valid if arguments are: s | r | t\n");
+      return 1;
+    }
+
+  mode = util_find_env("mode");
+  if (!mode)
+    {
+      exit (EXIT_FAILURE);
+    }
+
+  if (if_cond() == 0)
+    /* Propagate negative condition */
+    cond = 0;
+  else
+    {
+      switch (argv[1][0])
+	{
+	case 's': /* Send mode */
+	  cond = strcmp(mode->value, "send") == 0;
+	  break;
+	case 'r': /* Read mode */
+	  cond = strcmp(mode->value, "send") != 0;
+	  break;
+	case 't': /* Reading from a terminal */
+	  cond = is_terminal;
+	  break;
+	default:
+	  fprintf(ofile, "valid if arguments are: s | r | t\n");
+	  return 1;
+	}
+    }
+  _cond_push(cond);
+  return 0;
+}
+
+
+int
+mail_else (int argc, char **argv)
+{
+  int cond;
+  if (_cond_level == 0)
+    {
+      fprintf(ofile, "else without matching if\n");
+      return 1;
+    }
+  cond = _cond_pop();
+  if (_cond_level == 0)
+    cond = !cond;
+  _cond_push(cond);
+  return 0;
+}
+
+int
+mail_endif (int argc, char **argv)
+{
+  if (_cond_level == 0)
+    {
+      fprintf(ofile, "endif without matching if\n");
+      return 1;
+    }
+  _cond_pop();
   return 1;
 }
+
+void
+mail_set_is_terminal(int val)
+{
+  is_terminal = val;
+}
+
+int
+mail_is_terminal(void)
+{
+  return is_terminal;
+}

@@ -17,14 +17,162 @@
 
 #include "mail.h"
 
+static unsigned int
+z_lines()
+{
+  struct mail_env_entry *ep = util_find_env("screen");
+  size_t n;
+  
+  if (ep && ep->value && (n = atoi(ep->value)) != 0)
+    return n;
+  return util_getlines();
+}
+
+/* Scroll directions */
+#define D_BWD  -1 /* z- */
+#define D_NONE 0  /* z. */
+#define D_FWD  1  /* z+ */
+
 /*
- * z [+|-]
+ * z [+|-|. [count]]
+ * Optional [count] specifies number of pages to skip before
+ * displaying from lines. Default is 1.
+ * . modifier causes command to redisplay the current page, i.e.
+ * starting from the current message.
  */
 
+static int
+z_parse_args(int argc, char **argv, int *return_count, int *return_dir)
+{
+  int count = 1;
+  int mul = 1;
+  int dir = D_FWD;
+  int an = 0;
+  char *argp = NULL;
+
+  argp = &argv[an][1];
+  if (*argp == 0)
+    {
+      an++;
+      if (an < argc)
+	argp = argv[an];
+    }
+
+  if (*argp)
+    {
+      switch (*argp++)
+       {
+       case '+':
+	 break;
+       case '-':
+	 dir = D_BWD;
+	 break;
+       case '.':
+	 dir = D_NONE;
+	 break;
+       default:
+	 fprintf(ofile, "Bad arguments for the scrolling command\n");
+	 return 1;
+       }
+
+      if (*argp == 0)
+	{
+	  an++;
+	  if (an < argc)
+	    argp = argv[an];
+	}
+
+      argc -= an;
+ 
+      if (argc > 1)
+	{
+	  fprintf(ofile, "Too many arguments for the scrolling command\n");
+	  return 1;
+	}
+      
+      if (argp && *argp)
+	{
+	  if (dir == D_NONE)
+	    {
+	      fprintf(ofile, "argument no applicable for z.\n");
+	      return 1;
+	    }
+
+	  if ((mul = atoi(argp)) == 0)
+	    {
+	      fprintf(ofile, "Bad number of pages\n");
+	      return 1;
+	    }
+	}
+
+   }
+ 
+ *return_count = mul * count;
+ *return_dir = dir;
+ 
+ return 0;
+}
+
 int
 mail_z (int argc, char **argv)
 {
-  fprintf (ofile, "Function not implemented in %s line %d\n",
-	   __FILE__, __LINE__);
+  unsigned int i, nlines;
+  unsigned int pagelines = z_lines();
+  int count;
+  int dir;
+  
+  if (z_parse_args(argc, argv, &count, &dir))
+    return 1;
+
+  nlines = pagelines;
+  
+  count *= pagelines;
+  switch (dir)
+    {
+    case D_BWD:
+      if (cursor < nlines)
+	{
+	  fprintf(stdout, "On first screenful of messages\n");
+	  return 0;
+	}
+      if (cursor < count)
+	cursor = 1;
+      else
+	cursor -= count;
+      break;
+
+    case D_FWD:
+      if (cursor + pagelines > total)
+	{
+	  fprintf(stdout, "On last screenful of messages\n");
+	  return 0;
+	}
+
+      cursor += count;
+      
+      if (cursor + nlines > total)
+	nlines = total - cursor;
+  
+      if (nlines <= 0)
+	{
+	  fprintf(stdout, "On last screenful of messages\n");
+	  return 0;
+	}
+
+    case D_NONE:
+      break;
+    }
+  
+  realcursor = cursor;
+  
+  for (i = 0; i < nlines; i++)
+    {
+      if (mail_from(0, NULL))
+	break;
+      cursor++;
+    }
+
+  cursor = realcursor;
+  
   return 1;
 }